Don't return reference on copy assignment operators

We prefer to prevent using chained assignment (`T a = b = c = T();`) as this
can lead to confusing code and subtle bugs.

According to https://en.wikipedia.org/wiki/Assignment_operator_(C%2B%2B), C++
allows any arbitrary return type, so this is standard compliant.

This could be re-assessed if/when we have an actual need for a behavior more
akin to that of the C++ STL, for now this PR simply changes a handful of
cases which were inconsistent with the rest of the codebase (`void` return
type was already the most common case prior to this commit).

6 files changed, 9 insertions, 16 deletions

diff --git a/modules/gdscript/gdscript_function.h b/modules/gdscript/gdscript_function.h
index 9d076a8e4c..e1ed71a268 100644
--- a/modules/gdscript/gdscript_function.h
+++ b/modules/gdscript/gdscript_function.h
@@ -192,7 +192,7 @@ public:
 
 	GDScriptDataType() = default;
 
-	GDScriptDataType &operator=(const GDScriptDataType &p_other) {
+	void operator=(const GDScriptDataType &p_other) {
 		kind = p_other.kind;
 		has_type = p_other.has_type;
 		builtin_type = p_other.builtin_type;
@@ -203,7 +203,6 @@ public:
 		if (p_other.has_container_element_type()) {
 			set_container_element_type(p_other.get_container_element_type());
 		}
-		return *this;
 	}
 
 	GDScriptDataType(const GDScriptDataType &p_other) {
diff --git a/modules/gdscript/gdscript_parser.h b/modules/gdscript/gdscript_parser.h
index af9b973ada..2f05b4b948 100644
--- a/modules/gdscript/gdscript_parser.h
+++ b/modules/gdscript/gdscript_parser.h
@@ -203,7 +203,7 @@ public:
 			return !(this->operator==(p_other));
 		}
 
-		DataType &operator=(const DataType &p_other) {
+		void operator=(const DataType &p_other) {
 			kind = p_other.kind;
 			type_source = p_other.type_source;
 			is_constant = p_other.is_constant;
@@ -221,7 +221,6 @@ public:
 			if (p_other.has_container_element_type()) {
 				set_container_element_type(p_other.get_container_element_type());
 			}
-			return *this;
 		}
 
 		DataType() = default;
diff --git a/modules/mono/editor/bindings_generator.h b/modules/mono/editor/bindings_generator.h
index 51a27ee934..a7879e96c8 100644
--- a/modules/mono/editor/bindings_generator.h
+++ b/modules/mono/editor/bindings_generator.h
@@ -598,7 +598,7 @@ class BindingsGenerator {
 
 	private:
 		NameCache(const NameCache &);
-		NameCache &operator=(const NameCache &);
+		void operator=(const NameCache &);
 	};
 
 	NameCache name_cache;
diff --git a/modules/mono/godotsharp_dirs.cpp b/modules/mono/godotsharp_dirs.cpp
index 24bd1ed492..2b4cc7fcc3 100644
--- a/modules/mono/godotsharp_dirs.cpp
+++ b/modules/mono/godotsharp_dirs.cpp
@@ -229,9 +229,6 @@ private:
 #endif
 	}
 
-	_GodotSharpDirs(const _GodotSharpDirs &);
-	_GodotSharpDirs &operator=(const _GodotSharpDirs &);
-
 public:
 	static _GodotSharpDirs &get_singleton() {
 		static _GodotSharpDirs singleton;
diff --git a/modules/mono/mono_gc_handle.h b/modules/mono/mono_gc_handle.h
index d0e51d159f..a18a4ce646 100644
--- a/modules/mono/mono_gc_handle.h
+++ b/modules/mono/mono_gc_handle.h
@@ -56,13 +56,12 @@ struct MonoGCHandleData {
 
 	void release();
 
-	MonoGCHandleData &operator=(const MonoGCHandleData &p_other) {
+	void operator=(const MonoGCHandleData &p_other) {
 #ifdef DEBUG_ENABLED
 		CRASH_COND(!is_released());
 #endif
 		handle = p_other.handle;
 		type = p_other.type;
-		return *this;
 	}
 
 	MonoGCHandleData(const MonoGCHandleData &) = default;
diff --git a/modules/mono/mono_gd/gd_mono_log.cpp b/modules/mono/mono_gd/gd_mono_log.cpp
index 179bbfb40c..bcdcd6623b 100644
--- a/modules/mono/mono_gd/gd_mono_log.cpp
+++ b/modules/mono/mono_gd/gd_mono_log.cpp
@@ -121,12 +121,10 @@ void GDMonoLog::_delete_old_log_files(const String &p_logs_dir) {
 
 	ERR_FAIL_COND(da->list_dir_begin() != OK);
 
-	String current;
-	while ((current = da->get_next()).length()) {
-		if (da->current_is_dir()) {
-			continue;
-		}
-		if (!current.ends_with(".txt")) {
+	String current = da->get_next();
+	while (!current.is_empty()) {
+		if (da->current_is_dir() || !current.ends_with(".txt")) {
+			current = da->get_next();
 			continue;
 		}
 
@@ -135,6 +133,7 @@ void GDMonoLog::_delete_old_log_files(const String &p_logs_dir) {
 		if (OS::get_singleton()->get_unix_time() - modified_time > MAX_SECS) {
 			da->remove(current);
 		}
+		current = da->get_next();
 	}
 
 	da->list_dir_end();